A remarkable diversity of visual pathways has been shown to exist in addition to the classic retino-geniculo-striate pathway. Retinal fibers synapse in the midbrain, mesodiencephalic border (pretectum), thalamus and even hypothalamus, and in at least some instances, are suspected of encoding information in a manner quite distinct from that of optic tract fibers synapsing in the lateral geniculate body. Yet by comparison with the retino-geniculo-straite system, the so-called "extrageniculate pathways" are only imperfectly understood. It is the purpose of he proposed research to study the extrageniculate visual mechanism with particular reference to a) the links between its cortical and subcortical correspondents and b) the functional organization of the most prominent of its midbrain waystations, the superior colliculus. Work on thalamocortical relationships is aimed at understanding the general phenomenon of multiple representation of exteroceptive information within the cerebral cortex. Work on the superior colliculus attacks the problem of multiple sensory representation from the standpoint of the sensorimotor interface. The two themes of this work are closely related both in terms of theoretical motivation and of practical experimental demands. Principal reliance is to be placed upon the use of anterograde and retrograde neuroanatomical tracing methods but physiological recording techniques are to be incorporated into major aspects of the experimental design and the recently developed 2-deoxyglucose functional mapping technique will also be used. Most of the work is to be done on the cat but an extension of the work to the mascaque monkey is planned.